基于半导体激光器窄线宽光子微波信号获取

为了研究光注入半导体激光器(SL)产生的光子微波信号的性能, 基于SL的速率方程和光纤布喇格光栅(FBG)滤波理论, 采用数值仿真的方法进行了理论分析, 得到了各种注入参量下的光谱、功率谱和线宽, 并讨论了反馈参量对微波线宽的影响, 考虑到光注入下产生的微波线宽较宽, 进一步引入FBG光反馈窄化了微波信号的线宽。结果表明, 当SL仅在光注入作用下时, 通过改变注入参量, 可实现微波频率连续可调谐和微波强度最大化; 微波线宽随着反馈强度的增加逐渐变窄, 通过适当调节反馈参量可将微波线宽压缩到10kHz以下。该研究结果可为半导体激光器在光生微波中的应用提供一定的理论参考。     

Experimental Investigation on the Effect of Optical Source on Photonic Microwave Filter Performance

The filter frequency response and signal-to-noise ratio (SNR) capacity of fiber Bragg grating resonator based photonic microwave filter are investigated experimentally by using two lasers with different linewidths as optical sources. The effects of optical source on the photonic microwave filter performance are analyzed. The results show that when the laser linewidth is less than the filter free spectral range (FSR), the filter response is fluctuating and the SNR capacity decreases about 10dB.     

Polarization state rotation filter for optical generation of continuously tunable millimeter-wave signal employing an external intensity modulator

A method to generate a continuously tunable millimeter-wave signal employing an optical external intensity modulator and polarization state rotation filter (PSRF) is proposed. The technique is based on the optical heterodyne, the Mach–Zehnder modulator (MZM) is biased to suppress odd-order sidebands, and the polarization-dependent PSRF is used to filter the optical carrier. A concept-proof experiment system is built to demonstrate the generation of microwave signal by beating the generated two second-order optical components. The results show that a high purity tunable microwave signal with very narrow linewidth at four times the frequency of microwave drive signal can be obtained. Moreover, the generated signal does not suffer obvious phase-noise degradation after transmission through a 25-km SSMF link. The operation principle of PSRF and the effect of its performance on the generated electrical signal are also analyzed. The proposed technique based on PSRF is very easy to implement, flexible and cost-effective to generate continuously tunable millimeter-wave signals.     

基于相位调制器的宽带窄线宽的线性调频激光源的产生

提出了一种基于相位调制器(PM)和可调谐光滤波器产生线性调频激光信号的方法。该方法利用带有基频的微波线性调频信号作为相位调制器的驱动信号,窄线宽的激光种子源经相位调制器调制后产生一系列的宽带线性调频激光信号。通过可调谐光滤波器抑制其他边带保留所需阶次的线性调频激光信号。实验结果表明:当光滤波器保留正二阶调频激光信号时,获得了调频带宽为2 GHz、调频速率为6 THz/s的线性调频激光信号。在观测时间为1 ms时,测得的线性调频激光信号的瞬时线宽为3.2 kHz。该方法结构简单,易于实现,并且对调频连续波激光雷达、相干光谱分析等测量应用有重要意义。     

Pulsation stabilization and enhancement in self-pulsating laserdiodes

The authors report stabilization and enhancement of the optical pulses of self-pulsating laser diodes using a combination of self-injection locking and frequency locked loops. A record short term stability of one part in 1,500,000 (3 dB linewidth of less than 800 Hz at 1.3 GHz) was readily achieved with continuous tunability from 600 MHz to over 3 GHz (harmonics to over 12 GHz). The reduction in timing jitter resulted in a <10 dB improvement of the signal-to-noise ratio, making self-pulsating lasers a potential source of ultrastable picosecond pulses in both the optical and the electrical domains. The latter characteristics make self-pulsating lasers an attractive candidate for widely tunable microwave oscillators or sources for optical (electrical) sampling     

具有振动免疫特性光学谐振腔设计方法研究

窄线宽稳频激光是研制光学原子钟、引力波探测、 光学频率合成器以及低噪声微波源等研究的核心部分,由振动噪声引起的频率噪声已成为实 现具有更窄线宽、更高频率稳定度 激光的主要限制性因素。本文利用Ansys有限元分析的方法,通过优化参考腔的切割深度和 支撑位置以及ULE环的尺寸,使得腔镜在振动作用下保持平行同时腔镜各点均具有较低的振 动敏感度,避免了由于装配误差引起腔长变化的问题。在对光学参考腔几何尺寸优化设计后,对光学谐振腔不同频率处的振动敏感度进行测试及分析,结果表明在最佳支撑位置下空间三轴方向的振动敏感度均可被抑制至 10－10 g－1量级,实验结果和仿真结果相吻合。此方法为振动免 疫结构腔体的设计提供了一种思路,也为进一步实现具有更高频率稳定度、更窄线宽激光奠 定了基础。     

Optical feedback stabilization of the intensity oscillations inultrahigh-frequency passively modelocked monolithic quantum-well lasers

The effect of optical feedback on the stability of the modelocking frequency of monolithic, passively modelocked semiconductor lasers at ~50 GHz is investigated. Optical feedback leads to linewidth narrowing, frequency pulling, and multiple modes of the intensity modulations in modelocked lasers, reminiscent of similar effects on the optical frequency in conventional continuous wave (CW) lasers. The narrowest observed line has a full-width-at-half-maximum (FWHM) of 56 kHz, which represents close to two orders of magnitude reduction of the linewidth compared to the situation without feedback. The effects of the optical feedback vary periodically as the length of the feedback delay is varied, with a periodicity that roughly matches the mode-locking wavelength. This wavelength is on the order of millimeters, which makes the mechanical stability of the optical feedback loop relatively uncritical     

Frequency and wavelength tunable optical microwave source based on a distributed Bragg reflector self-pulsation laser

A frequency and wavelength tunable self-pulsation laser based on DBR laser devices is reported for the first time.This laser generates continuous tunable optical microwave in the range of 1.87-21.81 GHz with 3-dB linewidth about 10 MHz by tuning the injection currents on the front and back gain sections,and exhibits wavelength tuning range from 1536.28 to 1538.73 nm by tuning the injection currents on the grating section.     

Phase-Conjugate External-Cavity Diode Laser

An external-cavity diode laser based on self-pumped phase-conjugate optical feedback is reported. An antireflection-coated diode laser is subjected to strong phase-conjugate feedback from a photorefractive Ce-doped$hboxBaTiO_3$crystal. This provides narrow laser linewidth and good stability. Inherent linewidth of 25 kHz and relative frequency stability of$1.5,times 10 ^-8$(at 100 s) are demonstrated. Due to phase-conjugate feedback, the laser is insensitive to mechanical drifts and misalignment of the feedback element.     

Mid-range coherent optical frequency domain reflectometry with aDFB laser diode coupled to an external cavity

The optical frequency of an external double cavity coupled laser diode was controlled via the phase of the feedback light. Strong linewidth and mode hopping reductions were obtained, extending coherent reflectometry with semiconductor sources to the range of hundreds of meters     

Oscillation center frequency tuning, quantum FM noise, and direct frequency characteristics in external grating loaded semiconductor lasers

Simple analytical expressions for the oscillation frequency, quantum FM noise spectrum, oscillation power spectrum, spectral linewidth, and direct optical frequency modulation efficiency in semiconductor lasers with external grating feedback are presented. Experimental results for the grating loaded AlGaAs lasers are in good agreement with the theoretical predictions. Remarkable reduction in spectral linewidth to less than 50 kHz is achieved by feeding back only 10^-3of the output power. Oscillation frequency stabilization, frequency jump behavior, and reduction in direct optical frequency modulation efficiency are also discussed.     

光纤光栅外腔半导体激光器特性的研究

对谐振式集成光学角速率传感器 IORS 的关键器件之一——大功率、窄线宽光源进行了分析与实验 .分析结果表明 ,为达到优于 1°/ h的分辨率 ,光源应选用线宽小于 1MHz的强反馈光纤光栅外腔半导体激光器 FBG- L D ;研究了 FBG- LD的单纵模机制和线宽压窄特性 ,着重考虑了反馈端面的残留反射率对 FBG- L D输出功率的影响 ,以及耦合效率对 FBG- L D线宽的影响 ;在实验研究中采用了大功率、窄线宽、单纵模的 FBG- L D,并应用于光纤谐振腔 ,实测的谐振腔的清晰度与理论计算值是一致的 .     

四波混频和级联四波混频效应产生的连续光频率梳

针对产生光频率梳需要锁模激光种子源的难题,创新性提出了用连续光源产生光频率梳,应用色散平坦高非线性光纤解决了宽光谱范围四波混频和级联四波混频效应的相位失配问题。通过实验展示了近40 nm带宽的光频率梳的形成,光频率梳由低功耗,低成本,连续波种子（法布里-珀罗激光器）生成,无需脉冲激光源。连续光频率梳是由在420 m零色散色散平坦高非线性光纤中的四波混频和级联四波混频效应产生的,频谱带宽扩展了近10倍,频率梳的线宽为4.3 MHz。     

Effect of optical feedback on 60-GHz colliding-pulse semiconductor mode-locked lasers

We have experimentally investigated on the effects of optical feedback on the performance of monolithic colliding-pulse passively mode-locked semiconductor lasers operating at 60 GHz, designed to be efficient sources of millimeter-wave electrical signals. The characteristics of the optical-to-electrical converted signal are investigated for a long and a short external cavity by means of an external photodiode and by using the saturable absorber of the device as an intracavity photodetector. For a power feedback ratio larger than 10/sup -3/, the linewidth of the millimeter-wave signal is severely broadened with respect to the value of 230 kHz measured in unperturbed conditions. We also report that optical feedback causes central frequency shift and instability, and a reduction of the useful colliding-pulse mode-locked operating region in the biasing parameters of the device.     

Impact of flicker noise and random-walk noise on a phase-lockedloop with finite propagation delay

Approximate expressions for the phase-error variance due to the nonwhite frequency noise of optical sources are derived to analyze the performance of optical phase-locked loops (PLL's). The approximation incorporates the loop propagation delay, which is inevitable in actual systems. The obtained expressions are in simple form and yield only 3% maximum error. Using the obtained expressions, the influence of the flicker frequency noise and the random-walk frequency noise on the laser linewidth requirements are discussed. By examining semiconductor lasers that have been reported, it is found, quantitatively, that the flicker frequency noise does not affect the linewidth requirements, even in the presence of finite loop propagation delay. The obtained approximate expressions are used to examine low-white-frequency-noise optical sources, such as solid-state lasers, and to yield the allowable values of flicker frequency noise and random-walk frequency noise     

FM noise and spectral linewidth reduction by incoherent opticalnegative feedback

An all-optical, stable, external feedback method, the incoherent optical negative feedback method, is proposed and demonstrated for spectral linewidth reduction and optical-frequency stabilization of distributed-feedback (DFB) lasers. The power-spectral density of frequency modulation (FM) noise is shown to be reduced in a wide range of up to several hundreds of megahertz. The linewidth and the optical-frequency drift are simultaneously experimentally reduced to about 140 kHz and less than 17 MHz, respectively. The frequency range of the effective FM noise reduction and the reduction ratio of the FM noise are up to 1 GHz and 22 dB, respectively     

基于受激布里渊散射的微波光载波信号光谱检测

提出一种基于受激布里渊散射检测微波光载波信号光谱的方法。利用受激布里渊散射窄线宽的特性,解决了调制的微波信号频率低于常用的光谱分析仪分辨率时无法检测微波光载波信号光谱的问题,获得了较高的光谱检测分辨率。     

Millimeter-Wave Signal Generation Using Two Cascaded Optical Modulators and FWM Effect in Semiconductor Optical Amplifier

A novel method of optical generation millimeter-wave (mm-wave) signals employing two cascaded optical modulators and four-wave-mixing effect in semiconductor optical amplifiers is proposed. This approach is capable of generating signals of four times, eight times, and 12 times microwave source frequency with high spectral purity and stability. A mm-wave of 42 GHz (12times fundamental) with a 3-dB linewidth less than 30 Hz and a phase noise less than 83 dBc/Hz at 10-kHz offset is obtained.     

Instability of coherence in semiconductor laser due to externalfeedback in hybrid-integrated optical waveguide components

The coherence instability of oscillation-frequency shift and spectrum-linewidth fluctuation of a distributed feedback (DFB) semiconductor laser due to reflected feedback from input or output facets in a butt-coupled waveguide device is theoretically analyzed. A low-loss butt-coupling method between a semiconductor laser and a waveguide device for hybrid-integrated optical components used in coherent optical-fiber systems is presented. The calculated results indicate that (1) the coherence instability of the DFB lasers is sensitive to external optical feedback, (2) feedback from the waveguide input facet affects the laser frequency and gain shifts, and (3) feedback from the output facet intensifies the linewidth fluctuations